Camera shutter screen stays closed

Hello,

I have an IPOD 4th gen and when opening the camera application, the shutter on the screen stays closed. Also, the screen seems to flicker a bit as if the app is trying to access the camera, but can't. So I replaced the rear-facing camera, and still no luck. Is it possible this is a software issue? Could the issue be with the front facing camera? Inquiring minds want to know.